title: NO adsorption behaviors of the MnOx catalysts in lean-burn atmospheres.
abstract: NO(x) emission control of lean-burn engines is one of the great challenges in the world. Herein, the MnOx model catalysts with the different calcination temperatures were synthesized to investigate their NO adsorbability for lean-burn exhausts. The transformation from (β-)MnO₂ to (α-)Mn₂O₃ following the increased calcination temperatures was evidenced from the viewpoint of the local atomic level. Among these samples, the one calcined at 550 °C containing the single α-Mn₂O₃ phase displayed the best NO adsorbability: NO was mainly adsorbed in the forms of NO/nitrites and NO₂/nitrates at the low and high temperatures, respectively; the NO oxidation ability displayed the volcano-shape following the increased operating temperatures, and reached the maximum, i.e. 92.4% of the NO-to-NO₂ conversion, at 250 °C. Moreover, this sample presented the efficiently reversible NO adsorption/desorption performance in alternative lean-burn/fuel-rich atmospheres, due to the weakly bonded NO(x) on it. The superficial oxygen species plays a critical role for the NO oxidation over α-Mn₂O₃. The consumed superficial oxygen could be further compensated by the gaseous and lattice oxygen therein. Our findings show that the α-Mn₂O₃ material is a promising NO(x) adsorber for lean-burn exhausts even at low operating temperatures.
authors.affiliation: School of Chemical Engineering & Technology, Tianjin University, Tianjin 300072, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Guo
authors.forename: Hui
authors.initials: H
authors.lastname: Xian
authors.forename: Qi-Feng
authors.initials: QF
authors.lastname: Li
authors.forename: Da
authors.initials: D
authors.lastname: Chen
authors.forename: Yi-Sheng
authors.initials: YS
authors.lastname: Tan
authors.forename: Jing
authors.initials: J
authors.lastname: Zhang
authors.forename: Li-Rong
authors.initials: LR
authors.lastname: Zheng
authors.forename: Xin-Gang
authors.initials: XG
authors.lastname: Li
mesh_terms: D000327:Adsorption; D000397:Air Pollution / Q000517:prevention & control; D001272:Atmosphere; D002384:Catalysis; D017895:Manganese Compounds / Q000737:chemistry*; D009569:Nitric Oxide / Q000737:chemistry*; D010087:Oxides / Q000737:chemistry*; D010100:Oxygen / Q000737:chemistry*; D017382:Reactive Oxygen Species; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature; D013997:Time Factors; D001335:Vehicle Emissions; D014961:X-Ray Diffraction
chemical_list: D017895:Manganese Compounds; D010087:Oxides; D017382:Reactive Oxygen Species; D001335:Vehicle Emissions; D009569:Nitric Oxide; C027424:manganese oxide; D010100:Oxygen
keywords: Adsorption; Desorption; Lean-burn; Manganese oxides; Nitrogen oxides